In general, a fluid pressure generating device comprising a motor and a liquid pump driven by the motor is provided in the following construction. That is, the liquid pump (hereinafter, referred to as a pump) and the motor that drives the pump (hereinafter, referred to as a motor) are formed independently of each other. Then the output shaft of the motor is coupled with the input shaft of the pump via a coupling so that driving force of the motor is transmitted to the pump (Japanese Utility Model Laid-Open Publication No. 61-116192).
However, when the pump and the motor are formed independently of each other as shown above, there has been a problem that noise would occur at the shaft coupling portion because of misalignment between the output shaft and the input shaft. In addition, the operating noise of the pump and the motor result in a great noise as a whole. Also, since the pump and the motor are directly coupled with each other in the axial direction, the resulting axial length would become rather long so that the fluid pressure generating device as a whole would be a large size which would be a disadvantage.
Thus, as shown in Japanese Patent Publication for opposition No. 46-32900, a fluid pressure generating device was proposed which has a motor 102 and a pump 103 both contained within one casing 101, so that noise reduction and device downsizing can be implemented.
In this device, as shown in FIG. 12, a rotor 104 of the motor 102, which rotor is formed of laminated steel sheets, is rotatably supported to a main shaft 130 secured to the casing 101, via a pair of bearings 131, 132. The rotor 104 is provided with a plurality of holes 105, to which holes 105 and sleeves 106 are fitted, so that a plurality of cylinders 107 are formed. Further, pistons 108 are slidably provided in the cylinders 107. On the other hand, cylinder port plate 111 having a kidney-shaped ports 110 is disposed on one axial side of the rotor 104. One axial one end of each sleeve 106 is fitted to the cylinder port plate 111. A seal member 112 is provided between the fitting portion of the cylinder port plate 111 and the outer periphery of a sleeve 106. By this arrangement, the sleeves 106 and the rotor 104 have such a degree of freedom that they can move in both the axial and tilt-rotating direction relative to the cylinder port plate 111. Outside the cylinder port plate 111, a valve plate 116 with a suction port (not shown) and a discharge port 115 is disposed. This valve plate 116 is fixedly provided to the casing 101. The cylinder port plate 111 is put into sliding contact with the sliding surface of the fixed valve plate 116 so as to be rotatable relative to the sliding surface. Meanwhile, on the other axial side of the rotor 104, a swash plate 122 is provided which has an inclined surface on which shoes 121 retaining the head portions of the pistons 108 will slide. Further, a pressure plate 123 is provided so as to be fitted to the sleeves 106 on the other axial end side of the sleeves 106. One end face of this pressure plate 123 is in close contact with an end face of the rotor 104. A spherical retainer 125 for retaining the shoes 121 is fitted to a spherical portion 124 at the front end of the pressure plate 123.
The fluid pressure generating device constructed as described above is in such a coupling structure that the fitting portion between the cylinder port plate 111 and each sleeve 106 has a degree of freedom. Therefore, the cylinder port plate 111 and each sleeve 106 will be caused to move to each other in the axial direction by pressure variation within each cylinder 107. Also, the number of rotations of the motor 102 will vary due to load variation of the pump 103. In accompaniment to this variation, the cylinder port plate 111 and each sleeve 106 will be caused to move to each other in the rotating direction. By such relative movement in both the axial and rotating direction, noise will be generated at the fitting portion between the cylinder port plate. 111 and each sleeve 106. In addition, because of abrasion resulting from the sliding movement of both members 111 and 106, expansion and contraction of the seal member 112 due to variation in the internal pressure of the cylinders 107, and other reasons, the various members may be remarkably shortened in life.
Internal pressure of the cylinders 107 causes the sleeves 106 and the rotor 104 to be pushed toward the direction away from the cylinder port plate 111. Also, a radial pushing force acts on the right end side of the rotor 104 as viewed in FIG. 12 from the swash plate 122 via the shoes 121 and the pistons 108, causing the rotor 104 to tilt. This pushing force is due to reaction force of the radial component of a pushing force which receives from each piston 108 pushing the swash plate 122. In particular, the front end of the pressure plate 123 is supported by the main shaft 130, whereas its rear end fitted to the sleeves 106 with a clearance. Yet, there is a clearance between the main shaft 130 and the rotor 104. Accordingly, the rotor 104 tilts due to the aforementioned pushing force that acts on the fitting portion between the pressure plate 123 and the sleeves 106, the degree of the tilt being more than a permissible deflection of the main shaft 130. As a result, the rotor 104 will rotate while repetitively tilting, so that the gap between the rotor 104 and a stator 134 becomes nonuniform. This makes the rotation unstable, bringing about noise and vibration. Further, since the cylinders 107 are formed by providing a plurality of holes 105 to the rotor 104 that is formed of laminated steel sheets, each steel sheet constituting the rotor 104 needs to be provided with a through hole. This would involve troublesome machining and assembling work. Moreover, it is necessary to provide the sleeves 106 for sealing the cylinders 107 as well as the cylinder port plate 111 for forming the kidney-shaped port 110 and the pressure plate 123 for supporting both ends of the sleeves 106. This would involve an increased number of part items and unfavorably troublesome assembling work.